Practical limits on positron accumulation and the creation of electron-positron plasmas

Abstract

Abstract. The tasks of accumulating large numbers of positrons, creating high-density positron plastnas, and confining electron-positron plasmas present a number of technical challenges. Some practical considerations and limitations of common confinement schemes are discussed. A novel design for a multi-ccll Penning-Malmberg trap is proposed for the accumulation of large numbers of positrons (e.g., > 1012 and T -05 cV). A method is dcscribed to create a Ilow-density, electronpositron plasma (e.g., it "-107 cmt 3) for basic plasma physics studies that uses a cotnhinatiom of radio-frequency and magnetic confincment. The possibilities for confinement of a hot (cc.. T > 10 keV) electron-positron plasma in a magnetic mirror arc also discussed.

Plasma and trap-based techniques for science with positrons

“…The particles would be cooled by inelastic vibrational collisions with a molecule such as CO 2 . Details of the cooling process are discussed by Greaves and Surko (2002b), and additional considerations, including heating due to lepton-neutral collisions, are discussed in Surko et al (2014). A limitation of the Penning-Paul approach is that practical rf field amplitudes restrict the confining potential to ≤ 10 V, which restricts studies to relatively cool, low-density plasmas.…”

“…As illustrated in Fig. 47, a cylindrical PM trap was proposed, but with rf on the confining end electrodes (as opposed to potentials) to provide the repulsive potential to confine particles with both sign of charge (Greaves and Surko, 2002b). Positive dc potentials could also be applied to the electrodes to aid in positron confinement, in this case using the electrons sacrificially.…”

Positron Plasmas in the Laboratory

“…The new positron accumulator has been the workhorse for all subsequent positron experiments conducted during the grant period. [1,3,9,15,23,25] Cold beam experiments. Immediately preceding this grant, we developed a new method to create cold positron and electron beams by carefully extracting the particles from a Malmberg-Penning trap.…”

A new path toward gravity experiments with antihydrogen

“…• the fast loading mode where the positrons are stored and cooled to 2 meV in a Greaves-Surko trap [16] and extracted in ∼ 10 µs. This fast extraction heats the positron beam.…”

“…When Greaves-Surko traps [14,15,16] are available with a capability to hold 10 12 positrons and provided that the neutral plasma can be held during the time required to empty the trap, one could produce a density of positronium of ∼ 0.3 10 14 cm −3 . An experiment to observe the stimulated annihilation process would then become feasible.…”